Apparatus for continuous tartar separation

ABSTRACT

A method and an apparatus for continuously separating tartar from wine or grape juice using a draft tube baffled (DTB) crystallizer 2 and a hydrocyclone 3. The DTB crystallizer 2 comprises a vessel 5, a draft tube 6 centered in the body 5, a stirrer and a cooling jacket 16, said stirrer producing a circulation of liquid along the draft tube. A liquid of wine or grape juice is continuously introduced from the bottom of the crystallizer 2 into the crystallizer 2 and entrained in the circulation together with seed crystals at a low temperature to crystallize tartar dissolved in the source liquid. Supernatant source liquid is overflown from the crystallizer 2 and separated by the hydrocyclone 3 into a chemically-stabilized product and a suspension in which a large amount of tartar crystals is contained. The suspension is continuously returned to the crystallizer 2 to keep seed crystals at a desired concentration in the crystallizer 2.

FIELD OF THE INVENTION

This invention relates to a method and an apparatus for continuouslyremoving tartar from wine or grape juice in order to prevent tartarprecipitation in their bottled products. More particularly, it relatesto a technique for reducing or eliminating tartar dissolved in a liquidby adding seed crystals to the liquid so as to cause secondarynucleation and promote crystal growth in the liquid, said seed crystalsbeing tartar which has been separated from the liquid and consistsprimarily of potassium hydrogentartrate. The technique provideschemically stabilized juice and wine products and maintains theircommercial value.

BACKGROUND OF THE INVENTION

Bottled wine often has tartar precipitates in the form of crystals onthe bottom of the bottle. Such precipitates occur between bottling andconsumption. These precipitates make the product unattractive toconsumers.

Various methods have been proposed for preventing tartar precipitates.Tartar precipitates have been removed by cooling, cation exchange, anionexchange, reverse osmosis, and electrodialysis. Also, tartarprecipitates have been inhibited by the use of additives.

Of the above methods, the cooling methods have been commonly used. Theother methods have not been used commercially, since they suffer fromvarious disadvantages.

A cooling method based on the primary nucleation of potassiumhydrogentartrate which is a major component of tartar, is known.However, this method requires the maintenance of supersaturatedsolutions by means of cooling for a long time to produce naturalnucleation. Thus, it cannot serve market demand immediately, and itrequires a large initial investment for cooling equipment and storageequipment.

Another cooling method is known which comprises increasing tartarconcentration by freezing and thickening wine to acceleratecrystallization. However, this method cannot steadily crystallize andremove tartar and requires additional freezing equipment. This stillfurther increases initial equipment cost.

To eliminate the above disadvantages, some cooling methods have beenproposed that comprise adding tartar seed crystals to a source liquid ofwine so as to cause secondary nucleation and grow tartar crystals in thesource liquid, and thereafter separating the tartar crystals. Theseseeding methods are divided into two categories: A first contact methodand a second carrier adhesion method. The first method is disclosed, forexample, in West German Patent DE No. 3244221C1 issued to Westfalia Co.This publication discloses a process in which seed crystals of potassiumhydrogentartrate and dipotassium DL-tartrate are also added toprecipitate and remove calcium ions which inhibit the growth of tartarcrystals. In Japanese Examined Patent Publication No. 39157/1982, issuedto Henkel and Co., a process is disclosed in which calcium carbonate isemployed together with the seed crystal material. The second method isdisclosed, for example, in Japanese Examined Patent Publication No.5157/1981, issued to Henkel and Co. This publication discloses a processin which tartar is extracted from wine through the adhesion of thetartar on carriers made of fiber, etc. The carriers carry the tartarcrystals to promote the extraction.

In the seeding methods, tartar dissolved in a source liquid iscrystallized with seed crystals, and then the resulting suspension isseparated into treated liquid and tartar crystals by use of mechanicalseparation means such as hydrocyclones, centrifuges and filters. Thetreated liquid is served as a product. A part of the tartar crystals isrecycled and utilized as seed crystals.

In these methods, the suspension in which tartar which has beenprecipitated together with seed crystals in a reaction vessel, isintroduced into separation means together with treated liquid, and thenis separated. In other words, these methods are batch processes whereinwhenever a treatment is conducted, a source liquid has to be introducedinto the reaction vessel and seed crystals also have to be added to thesource liquid. Therefore, these methods require a large amount of seedcrystals and thus require separation means having a large capacity suchas a centrifuge. Further, these methods based on the batch process arenot advantageous to operation or equipment, i.e., they require alarge-sized crystallizer or a number of crystallizers in order to treata large amount of source liquid.

Usually, the suspension is stood for about two weeks so as toprecipitate tartar crystals. In order to shorten such period for theprecipitation, Japanese Examined Patent Publication No. 39157/1982issued to Henkel and Co. suggests a continuous process wherein thesuspension is stood for 1 to 2 days, and thereafter supernatant isdischarged by use of auxiliary mechanical means. The process, however,additionally requires contact crystals to promote the precipitation ofcalcium tartrate resulting from the reaction of calcium carbonate andtartaric acid. It also requires a heating stage for promoting thereaction and requires the installation of intermediate plates and meansfor collecting gas generated in the crystallizing vessel. Therefore, itis apparent that the process requires complicated equipment andoperation.

Japanese Examined Patent Publication No. 5157/1981 issued to Henkel andCo. also suggests an apparatus which comprises a crystallizing vesseland a carrier which is as large as possible for installing it in thecrystallizing vessel, pulverized seed crystals preliminarily adhering tosaid carrier, means for scraping crystallized tartar during the process,and a conveyor which discharges precipitated tartar. However, thissystem is also complicated and is not advantageous to operation,equipment or maintenance.

For the purpose of solving the above-described problems of the seedingmethods and making it possible to efficiently and continuously conduct aseeding method without a batch process or large equipment, the presentinventors suggested a draft tube baffled crystallizer (hereinafterreferred to as DTB crystallizer) in Japanese Unexamined PatentPublication No. 69976/1987.

As shown in FIG. 3 of the accompanied drawings, the DTB crystallizer 100comprises a cylindrical vessel 101 which has an outlet 102 on its upperwall and an inlet 103 at its bottom, a draft tube 104 which is centeredin a lower half portion of the vessel 101 and supported by supportingmembers 105, 105', a stirrer which comprises a shaft 106 extending alongwith the longitudinal axis of the vessel 101, propellers 107, 107'mounted on the shaft 106 inside the draft tube 104 and a propeller 108mounted on the shaft 106 below the draft tube 104, and a cooling jacket109 which is disposed on the exterior wall of the vessel 101.

The DTB crystallizer attains three functions of crystallization,classification and clarification in a vessel by forming the followingtwo sections in the vessel in use. The first is a crystallizationsection wherein a source liquid is circulated along the draft tube at alow temperature so that tartar is crystallized involving seed crystalsas nuclei. The second is a calm section which is located in the upperportion of the crystallizer and is not disturbed by the circulation ofthe crystallization section. The classification function is effectedbetween the crystallization section and the calm section by allowingcrystals to sink from the calm section to the crystallization section.The DTB crystallizer is simple in structure, low in cost and easy tomaintain, and makes it possible to continuously separate tartar from asource liquid of wine or grape juice in a short time.

However, the rate of production has to be limited in order to form thetwo sections and maintain the functions of crystallization,classification and clarification in the DTB crystallizer. If the amountof a source liquid is increased in a continuous operation, thecirculation along the draft tube extends to the calm section so thattartar contaminates the treated liquid and the treated liquid becomeschemically unstabilized.

The DTB crystallizer would be replaced with another large-scaled similarcrystallizer rather than modified if the production capacity should beincreased.

OBJECT OF THE INVENTION

It is an object of the present invention to provide a method and anapparatus for continuously separating tartar from a source liquid byadding seed crystals to the source liquid, which are free from anylimited operation conditions and which ensure the effect of tartarseparation.

Other objects and advantages of the present invention will becomeapparent from the description set forth below.

SUMMARY OF THE INVENTION

The present invention relates a technique for separating tartar from asource liquid of wine or grape juice which has been processed at a lowtemperature in ordinary way. The technique conducts the crystallizationstage and the classification stage separately while those stages havebeen conducted in one and the same conventional DTB crystallizerdescribed above. The crystallization stage is conducted in acrystallizer having a draft tube. In the crystallizer, tartar which isdissolved in a source liquid, is crystallized with seed crystals addedto the source liquid. The seed crystals may be crystals which resultfrom the crystallization of a source liquid and consist primarily ofpotassium hydrogentartrate. The treated source liquid which overflowsfrom the upper portion of the crystallizer, is introduced into ahydrocyclone. A chemically stabilized product is obtained as the upwardstream from the hydrocyclone. The downward stream from the hydrocycloneis returned to the crystallizer so as to utilize the crystallized tartarcontained therein as seed crystals. Thus, the present invention cancontinuously separate tartar from a source liquid of wine or grapejuice.

In one aspect, the present invention provides a method for continuouslyremoving tartar from a source liquid of wine or grape juice by use ofseed crystals. The method employs a DTB crystallizer which comprises acrystallizing vessel and a draft tube. The draft tube is placed in acenter portion of the vessel so as to define an annular zone between theinner periphery of the crystallizing vessel and the outer periphery ofthe draft tube. The draft tube has a height of 1/2 to 1/4 the totalheight of the crystallizer. A downward or upward flow is produced insidethe draft tube, and a upward or downward flow is produced in the annularzone. The flow in the annular zone is slower than the flow inside thedraft tube. A source liquid of wine or grape juice is introduced fromthe bottom of the crystallizer into the crystallizer at a lowtemperature, and a suspension containing tartar crystals is added to thecrystallizer as seed crystals. The source liquid is circulated with thedownward flow and the upward flow along the draft tube with keeping theliquid at a low temperature to crystallize tartar dissolved in thesource liquid. The circulation comprises a fast downward or upward flowinside the draft tube, a slow upward or downward flow between the innerperiphery of said vessel and the outer periphery of said draft tube, afirst reversal flow above the draft tube and a second reversal flowbelow the draft tube. The source liquid is overflown from an upperportion of the crystallizer, and the overflown liquid is introduced intoa hydrocyclone. The upward stream output of the hydrocyclone isrecovered to obtain a product from which tartar crystals are removed.The downward stream output of the hydrocyclone is returned to thecrystallizer to be utilized as seed crystals.

At the end of operation, the source liquid which remains together withtartar crystals in the crystallizer, is discharged from the bottom ofthe crystallizer, and is introduced directly into the hydrocyclone.Then, the upward stream output of the hydrocyclone is recovered to thecontainer for treated liquid as a product from which tartar crystals areremoved. The downward stream output of the hydrocyclone is introducedinto a mechanical separator, and then is separated into a clarifiedliquid and a suspension in which tartar crystals are contained at a highconcentration. The clarified liquid is recovered to the container fortreated liquid as a product. The suspention is stored so as to be servedas seed crystals in subsequent operations.

In another aspect, the present invention provides an apparatus forremoving tartar from a source liquid of wine or grape juice. Theapparatus comprises a container for source liquid, a crystallizer, ahydrocyclone and a container for treated liquid.

The crystallizer comprises a crystallizing vessel, a draft tube, astirrer and a cooling jacket. The draft tube is disposed in a centerportion of the vessel so as to define an annular zone between the innerperphery of the crystallizing vessel and the outer periphery of saiddraft tube. The draft tube has a height of 1/2 to 1/4 the height of thevessel and has a cross section smaller than the annular zone. Thestirrer is adapted to produce a circulation of liquid along the drafttube. The cooling jacket is disposed on the outer periphery of thevessel. The vessel has an inlet for source liquid at the bottom thereof,an outlet for treated liquid in the upper portion thereof and an inletfor tartar suspension in the lower portion thereof.

The hydrocyclone has an outlet for upward stream on the top portionthereof, an outlet for downward stream on the bottom portion thereof andan inlet on the upper portion thereof.

The container for source liquid is connected via a conduit with theinlet for source liquid of the crystallizer. The outlet for treatedliquid of the crystallizer is connected via a conduit with the inlet ofthe hydrocyclone. The outlet for upward stream of the hydrocyclone isconnected via a conduit with the container for treated liquid. Theoutlet for downward stream of the hydrocyclone is connected via aconduit with the inlet for tartar suspension of the crystallizer.

These conduits form a main line for continuous operation.

The inlet for tartar suspention of the crystallizer is also connectedvia an auxiliary conduit with a container which stores a tartarsuspension so that the tartar suspension may be introduced as seedcrystals from that container into the crystallizer at the beginning ofoperation.

The inlet for source liquid of the crystallizer is also connected via anauxiliary conduit with the inlet of the hydrocyclone so that the sourceliquid which remains together with tartar crystals after operation, maybe introduced from the crystallizer directly into the hydrocyclone.

The outlet for downward stream of the hydrocyclone is also connected viaan auxiliary conduit with a mechanical separator so that the downwardstream may be separated into a clarified liquid and a suspension inwhich tartar crystals are contained at a high concentration. Themechanical separator has an auxiliary conduit which leads the clarifiedsuspension into the container for treated liquid and a conduit whichleads the suspension to the container for tartar suspension.

These auxiliary conduits may diverge via three-way valves from the mainline.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow sheet of a preferred embodiment of the apparatusaccording to the present invention.

FIG. 2 is a diagrammatic illustration of the DTB crystallizer used inthe embodiment of FIG. 1.

FIG. 3 is a diagrammatic illustration of a DTB crystallizer.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENT

In FIG. 1, an apparatus comprising a container for source liquid, acrystallizer, a hydrocyclone and a container for treated liquid, whichare generally indicated by the numerals 1, 2, 3 and 4, respectively. Thecontainer 1, the crystallizer 2, the hydrocyclone 3, and the container 4are connected in series by a main line. The main line comprises valvesand conduits such as pipes made of stainless steel and hoses. Theapparatus also comprises a separator and a container for seed crystalsuspension, which are indicated by the numerals 29 and 25, respectively.

As best shown in FIG. 2, the crystallizer 2 comprises a crystallizingvessel and a draft tube 6. The crystallizing vessel comprises an uprightcylindrical body 5 and a conical bottom. The body 5 is preferbly made ofstainless steel. The draft tube 6 is coaxially disposed in a centerportion inside of the body 5. The draft tube 6 is supported byappropriate supporting members 7 which extend from the inner wall of thebody 5 inwardly of the body 5. Preferably, the draft tube 6 has a heightof 1/2 to 1/4 the height of the total height of the crystallizer 2 andhas a diameter of 1/2 to 1/3 the diameter of the body 5. Thecrystallizer further comprises a stirrer which is generally indicated bythe numeral 12. The stirrer 12 comprises a shaft 8 and propellers 9, 10and 10'. The shaft 8 extends along the common axis of the body 5 and thedraft tube 6 from the outside of the top portion to the vicinity of theconical bottom of the body 5. The propeller 9 is mounted on the bottomend of the shaft 8 so as to be located adjacent to the conical bottom ofthe crystallizer 2. The propeller 10 is mounted on the bottom portion ofthe shaft 8 surrounded by the draft tube 6. The propeller 10' is mountedon the top portion of the shaft 8 surrounded by the draft tube 6. Ifnecessary, two or more of propellers may be provided inside of the drafttube 6. The stirrer 12 is rotated at an appropriate speed by driving theshaft 8 with a driving means such as a motor mounted on the top of thecrystallizer 2.

In this embodiment, the propeller 9 is adapted to make liquid in theconical bottom of the body 5 flow upwardly through the annular zonedefined between the inner periphery of the body 5 and the outerperiphery of the draft tube 6 into the portion above the draft tube 6,and the propellers 10, 10' are adapted to make the liquid inside thedraft tube 6 flow downwardly. Thus, a circulation comprising an upwardflow through the annular zone, a downward flow through the inside of thedraft tube 6, a first reversal flow below the draft tube 6 and a secondreversal flow above the draft tube 6, is effected. However, thepropellers 9, 10 and 10' may be adapted to effect the inversecirculation.

The crystallizer 2 has an inlet 13 for source liquid at the bottom ofthe body 5, an outlet 14 for treated liquid on the upper wall of thebody 5 and an inlet 15 for tartar suspension on the lower wall of thebody 5. The crystallizer 2 has a cooling portion 16 such as coolingjacket on its exterior wall. Insulation materials are also provided withthe entire surface of the exterior wall. Coolant is supplied to thecooling portion 16 to maintain liquid at a low temperature inside thecrystallizer 2.

The hydrocyclone 3 is a multi-hydrocyclone which combines a plurality ofhydrocyclones together so that the capacity may be varied depending onthe amount of liquid to be treated. However, the hydrocyclone 3 may bereplaced with any one of the hydrocyclones which have conventionallybeen used. The hydrocyclone 3 has an outlet 17 for upward stream at itstop, an outlet 18 for downward stream at its bottom and an inlet 20 onits upper wall.

The container 1 stores a source liquid of wine or grape juice. Thecontainer 4 stores a product of wine or grape juice which has beenchemically stabilized according to the present invention.

A conduit 19 connects the container 1 with the inlet 13 for sourceliquid of the crystallizer 2. A conduit 21 connects the outlet 14 fortreated liquid of the crystallizer 2 with the inlet 20 of thehydrocyclone 3. A conduit 22 connects the outlet 17 for upward stream ofthe hydrocyclone 3 with the container 4. A conduit 23 connects theoutlet 18 for downward stream of the hydrocyclone 3 with the inlet 15for tartar suspension of the crystallizer 2. The conduits 19, 21, 22 and23 are made of stainless steel.

A conduit 24 connects the conduit 19 and the conduit 21 at three-wayvalves 31 and 32, respectively. After operation, the valves 31 and 32are changed so as to lead tartar suspension remaining in thecrystallizer 2 to the hydrocyclone 3 via the conduit 24. A conduit 26which is led from the container 25, connects the conduit 23 at athree-way valve 30. The container 25 stores a tartar suspension having ahigh concentration, which is recovered from the treated liquid and issupplied as seed crystals to the crystallizer 2 when operation isstarted. At the beginning of operation, the valve 30 is changed so as tolead the suspension contained in the container 25 to the conduit 23 viathe conduit 26 and to supply seed crystals to the crystallizer 2. Theconduit 23 also connects a separator 29 via a three-way valve 30'. Theseparator 29 is a screw decanter. During continuous operation, the valve30' leads the downward stream of the hydrocyclone 3 to the crystallizer2 via the conduit 23. When the operation is over, the valve 30' ischanged to lead the downward stream into the separator 29. The separator29 separates the downward stream into a liquid which is free from tartarand a tartar suspension having a high concentration. The treated liquidis recovered to the container 4. The tartar suspension is recovered tothe container 25.

In order to lead source liquid to the crystallizer 2 with keeping it ata low temperature, a cooling means 27 is provided on the conduit 19. Abuffer tank 28 and a pump 33 are interposed in the conduit 21. Thebuffer tank 28 receives the treated liquid overflowing from thecrystallizer 2 and regulates the amount of the liquid which isintroduced via the pump 33 into the hydrocyclone 3.

Operation

With reference to FIGS. 1 and 2, the operation of the apparatusaccording to the present invention is now set forth.

A source liquid of wine or grape juice which tends to precipitate tartarbetween bottling and consumption, is stored in the container 1. Thesource liquid is conveyed through the conduit 19 to the inlet 13 of thecrystallizer 2, while the source liquid is kept at a temperature of 0 to-3° C. by the cooling means 27. The source liquid which has beenintroduced into the crystallizer 2, is kept at a low temperature of 0 to-3° C. by virtue of the cooling portion 16 and the insulating materialwhich covers the entire exterior wall of the crystallizer 2. At the sametime when the source liquid is introduced into the crystallizer 2,tartar suspension is introduced from the container 25 as seed crystalsthrough the conduits 26 and 23 to the inlet 15 of the crystallizer 2.Although the amount of the seed crystals to be added depends onproperties and temperature of source liquid, it is preferably 7 to 8grams per liter of source liquid when the source liquid has atemperature of about 0° C., and 3 to 4 grams per liter of source liquidwhen the source liquid has a temperature of about -3° C.

The stirrer 12 is started after source liquid has been charged to thelevel of the propeller 10. In other words, the propeller 10 and 10'located inside the draft tube and the propeller 9 located at the lowerportion of the crystallizer 2 are rotated by the shaft 8 driven by themotor 11. Since the propeller 9 and the propellers 10, 10' are adaptedto force the liquid to flow in opposite direction, the liquid flowsdownwardly inside the draft tube 6 and upwardly in the annular zonedefined between the draft tube 6 and the body 5 of the crystallizer, asshown in arrows in FIG. 2. Since the draft tube 6 has a diameter of 1/2to 1/3 the diameter of the body 5 and thus the cross sectional area ofthe annular zone is designed to be larger than that of the draft tube 6,the liquid flows upwardly in the annular zone at a linear velocityslower than inside the draft tube. During the upward and downward flows,secondary nucleation is induced by the seed crystals, and nuclei oftartar crystals occur particularly in the draft tube. Since tartarcrystals which have grown are prevented by the propeller 9 fromprecipitating and accumulating on the conical bottom of the crystallizer2, they are entrained by the upward flow and circulated to the upperportion of the crystallizer so that crystallization is uniformlyeffected in the crystallizer.

In this way, the source liquid which has been introduced into the bottomof the crystallizer, is treated to reduce the concentration of tartardissolved therein. After residing and circulating in the crystallizer 2,the treated liquid is overflown from the outlet 14 located on the upperwall of the crystallizer 2 and supplied via the conduit 21 to the inlet20 of the hydrocyclone 3. If the treated liquid overflowing from thecrystallizer 2 is supplied directly to the hydrocyclone 3 via a pump 33,it is preferred that the liquid is supplied by way of a buffer tank 28to the pump 33 so that variation of the amount of the treated liquid ismoderated.

The treated liquid overflowing from the crystallizer contains tartarwhich has been crystallized in the crystallizer 2. The treated liquid isseparated by the hydrocyclone 3 into tartar crystals and product liquidby virtue of its centrifugal function. The product liquid is dischargedthrough the outlet 17 for upward stream, and then is conveyed via theconduit 22 to the container 4. The product liquid is chemicallystabilized so as not to occur precipitates between bottling andconsumption and thus maintains high commercial value.

On the other hand, a suspension in which a large amount of tartarcrystals are contained, is discharged from the outlet 18 for downwardstream to the outside of the hydrocyclone 3. The suspension is conveyedvia the conduit 23 and is continuously introduced through the inlet 15into the crystallizer 2 so that tartar crystals contained in thesuspension are recycled to be used as seed crystals and to prevent theconcentration of seed crystals in the crystallizer 2 from decreasing.

It is apparent from the above description that the present inventionmakes it possible to continuously process the source liquid stored inthe container for source liquid and obtain the product in which tartardissolved is reduced or eliminated, and further makes it possible torecycle seed crystals only if they are added from the outside at thebeginning of operation so as to make it unnecessary to add seed crystalsfrom the outside during operation.

When operation is finished, the three-way valves 31 and 32 are changedto connect the inlet 13 of the crystallizer 2 with the inlet 19 of thehydrocyclone 3 via the conduit 24. Also, the three-way valves 30 and 30'are respectively changed to close the conduit 23 which connects theoutlet 18 for downward stream of the hydrocyclone 3 with the inlet 15for tartar suspension of the crystallizer 2 and to connect the outlet 18for downward stream with the separator 29. Then, the liquid whichremains with tartar suspending in the crystallizer 2 after treatment hasbeen finished, is led to the inlet 17 of the hydrocyclone 3. The liquidwhich has been introduced into the hydrocyclone 3, is separated byvirtue of centrifugal function into a suspension in which a large amountof tartar crystals is contained and a liquid from which tartar crystalshave been removed. The latter is discharged from the outlet 17 forupward stream and collected in the container 4. The former is dischargedfrom the outlet 18 for downward stream and introduced into the separator29. Then, the former is further separated by the separator 29 into aliquid from which tartar crystals have been removed and a suspension inwhich tartar is contained at a high concentration. That liquid isrecovered by the container 4. That suspension is recovered by thecontainer 25.

EXAMPLE

An experiment was conducted using the apparatus as shown in FIG. 1.

One hundred kiloliters of source liquid of wine was charged into acontainer 1 for source liquid having a volume of 100 kiloliters. Theoutlet located on the bottom of the container 1 was opened to supply thesource liquid at a rate of 20 kiloliters per hour to a crystallizer 2via a conduit 19 and an inlet 13 for source liquid. In the way to thecrystallizer 2, the source liquid was cooled to -3° C. by a plate-typecooler 27 which was located on the conduit 19.

The body 5 of the crystallizer 2 was made of stainless steel and had avolume of 20 kiloliters. The draft tube 6 was made of stainless steeland had a height of 150 cm and a diameter of 150 cm. The draft tube 6was located in the center portion of the crystallizer by supporting itwith supporting members 7. The propellers 10 and 10' were mounted on ashaft 8 inside the draft tube adjacent the bottom end of the draft tubeand adjacent the top end of the draft tube, respectively. The propeller9 was mounted on the shaft 8 so as to be arranged adjacent the bottom ofthe crystallizer 2. To the cooling jacket 16 which comprises insulatingmaterials covering the entire exterior wall of the crystallizer 2,coolant was supplied to maintain the source liquid at -3° C. in thecrystallizer 2.

After the source liquid had been supplied with the crystallizer 2 to thelevel of the propeller 10, 60 kilograms of tartar crystals were suppliedto the crystallizer 2 by changing the valve 30 to connect the conduit 26with the inlet 15 of the crystallizer 1 and to introduce from thecontainer 25 into the crystallizer 2 a seed crystal suspensioncontaining tartar crystals which had resulted from a source liquid andconsisted of pottasium hydrogentartrate. After the suspension had beensupplied, the valve 30 was closed.

Then, the motor 11 mounted on the top of the crystallizer 2 was startedto rotate the propellers 9, 10 and 10' at 100 rpm or less. Thepropellers 10 and 10' produced a downward flow of the source liquidinside the draft tube 6 as shown by a downward arrow in FIG. 2. Thepropeller 9 produced a slow upward flow having a linear speed of 0.6meter/hour of the source liquid in the annular zone defined between theinner periphery of the body 5 and the outer periphery of the draft tube6 as shown by an upward arrow in FIG. 2. Thus, a circulation of thesource liquid along the draft tube 6 was produced, in whichcrystallization of tartar was promoted by virtue of secondary nucleationinduced by seed crystals and crystal growth of seed crystals.

While the source liquid was introduced into the crystallizer 2 at a rateof 20 kiloliters per hour for one hour, supernatant source liquid wasoverflown from the outlet 14. The overflown liquid was recovered to thebuffer tank 28 and then introduced through the inlet 20 into the amulti-hydrocyclone 3 by way of the conduit 21 and the pump 33. Themulti-hydrocyclone 3 was the one in which five standard hydrocycloneswere put together. The multi-hydrocyclone 3 was operated to separate theoverflown liquid from tartar crystals suspended therein. Wine from whichtartar crystals had been removed, was discharged from the outlet 17 forupward stream and then recovered through the conduit 22 to the container4.

Wine in which a large amount of tartar was contained, was dischargedfrom the outlet 18 for downward stream and returned to the crystallizer2 by way of the conduit 23 and the inlet 15 to keep the concentration oftartar at 3 grams/liter or more in the crystallizer 2.

Until the container 1 became empty, the above operation was continuouslyconducted for about 5 hours to produce 80 kiloliters of treated wine inthe container 4.

After the above stage, the valve 31 was changed so that the inlet 13 forsource liquid is disconnected with the conduit 19 and is connected withthe conduit 24. Also, the valve 32 is changed to connect the conduit 24with the inlet 20 of the multi-hydrocyclone. Also, the valve 30 wasclosed, and the valve 30' was changed to lead the downward stream fromthe multi-hydrocyclone 3 to a screw decanter 29. Then, the pump 33 wasstarted to discharge the liquid which remained with tartar crystalssuspending in the crystallizer 2 from the inlet 13 and introduce thesame liquid into the inlet 20 of the multihydrocyclone 3 via the conduit24. The multi-hydrocyclone 3 was operated to separate the liquid into anupward stream of wine from which tartar crystals were removed and adownward stream of wine in which a large amount of tartar crystals wascontained.

The upward stream of wine from which tartar crystals were removed, wasconveyed from the outlet 17 of the multi-hydrocyclone 3 via the conduit22 to the container 4 for treated liquid.

The downward stream of wine in which tartar was contained, was furtherseparated by the screw decanter 29 into a wine from which tartarcrystals were removed and a wine in which tartar crystals were containedat a high concentration. The former was conveyed to the container 4 fortreated liquid via conduit. The latter was conveyed to the container 25for tartar suspension via conduit.

The above stages were completed in six hours, and 100 kiloliters of winefrom which tartar dissolved was reduced, was obtained.

The above description deals with a crystallizer having a single drafttube. Alternatively, a crystallizer may have a plurarity of narrow drafttubes which are placed end to end at intervals and/or side by side sothat the crystallizer processes even a small amount of liquid.

Caveat

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that, within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

We claim:
 1. An apparatus for removing tartar from wine or grape juice,said apparatus comprising:(a) a container for source liquid; (b) acrystallizer which comprises a crystallizing vessel, a draft tube, astirrer and a cooling jacket, said draft tube being disposed in a centerportion of the vessel so as to define an annular zone between the innerperiphery of said vessel and the outer periphery of said draft tube, andsaid draft tube having a height of 1/2 to 1/4 the height of the vesseland a cross section smaller than the annular zone, said stirrer beingadapted to produce a circulation of liquid along the draft tube, saidcooling jacket being disposed on the outer periphery of the vessel, andsaid vessel having an inlet for source liquid at the bottom thereof, anoutlet for treated liquid in the upper portion thereof and an inlet fortartar suspension in the lower portion thereof; (c) a hydrocyclone whichhas an outlet for upward stream on the top portion thereof, an outletfor downward stream on the bottom portion thereof and an inlet on theupper portion thereof; and (d) a container for product liquid; whereinsaid container for source liquid is connected with the inlet for sourceliquid of the crystallizer, said outlet for treated liquid of thecrystallizer is connected with the inlet of the hydrocyclone, saidoutlet for upward stream of the hydrocyclone is connected with thecontainer for treated liquid, and said outlet for downward stream of thehydrocyclone is connected with the inlet for tartar suspension of thecrystallizer.
 2. An apparatus according to claim 1 which furthercomprises a container for seed crystals and means for connecting saidcontainer for seed crystals with a conduit via which the outlet fordownward stream of the hydrocyclone is connected with the inlet fortartar suspension of the crystallizer when necessary.
 3. An apparatusaccording to claim 1 which further comprises means for connecting theinlet for source liquid of the crystallizer with the inlet of thehydrocyclone when necessary.
 4. An apparatus according to claim 1 whichfurther comprises a separator which separates the downward stream of thehydrocyclone from tartar crystals and means for connecting the outletfor downward stream of the hydrocyclone with the separator whennecessary.